CAPE CANAVERAL (AP) – NASA began another countdown Wednesday for space shuttle Endeavour, but stormy weather could stall the weekend launch.

The space agency will try to launch Endeavour on Saturday night, following a pair of delays last month caused by a hydrogen gas leak. The leak has since been plugged; a fueling test validated the repairs last week. But now, launch controllers will have to deal with thunderstorms.

Forecasters on Wednesday put the odds of acceptable weather at just 40 percent for a Saturday evening launch. Conditions improve only slightly on Sunday.